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Audio for Next-Generation Broadcast Services: The Dolby MS10 Multistream Decoder Solution · PDF file 2010-04-21 · Audio for Next-Generation Broadcast Services: The Dolby MS10 Multistream

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  • 1Dolby Multistream Decoder Technical Paper

    Technical Paper

    Audio for Next-Generation Broadcast Services: The Dolby MS10 Multistream Decoder Solution

    Summary

    • Two multichannel audio formats—Dolby® Digital Plus and Dolby Pulse—are attractive for next-generation broadcasts for different reasons, and it is likely that both will be used for new European services.

    • Key new European HDTV receiver specifications include both Dolby Digital Plus and Dolby Pulse.

    • Dolby is developing a new multiformat audio decoder implementation that will ease the inclusion of dual decoders in new receivers.

    Broadcaster and Operator Requirements

    Over the last 18 months, various European industry groups such as DVB, EBU, EICTA, and a number of national HDTV specification forums have considered the selection of audio coding systems for next-generation broadcast applications, including HDTV broadcasts, using MPEG-4 video. In general, these considerations have highlighted two standardized audio coding systems as particularly suited to next-generation transmissions: Dolby Digital Plus (also known as E-AC-3) and Dolby Pulse (Dolby’s implementation of aacPlus or HE AAC). The EBU Project Group D/MAE, for example, concluded that the two coding formats are the best candidates for broadcasting HDTV audio services via satellite, cable, terrestrial, and IPTV networks.

    Due to the diverse market requirements of different broadcasters/operators and the differing feature sets of these technologies, it has not generally been possible for these groups to recommend a single audio system that suits all applications. For example, Dolby Digital Plus currently offers comprehensive support for 5.1-channel sound as well as advanced metadata support. Dolby Pulse will also offer this support in the near future, along with its already formidable coding efficiency, which today enables quality stereo services to be transmitted at extremely low data rates.

    In addition, over 200 European TV services already broadcast with conventional Dolby Digital audio, so next-generation receivers typically need to be compatible with this format.

    While Dolby Laboratories intends to distribute a commercial release of the Dolby Multistream Decoder, Dolby Laboratories reserves the right, at any time, not to release a commercial release of Dolby Multistream Decoder or, if it does so, to alter prices, features, specifications, capabilities, functions, licensing terms, release dates, general availability, or other characteristics of the commercial release.

  • 2Dolby Multistream Decoder Technical Paper

    Technical Paper

    European HDTV Receiver Specifications

    As DVB does not specify which audio coder should be used for next-generation broadcasts, various broadcaster/manufacturer groups have recently worked collaboratively to gain consensus on the formats desired by broadcasters, which will then be included in European receivers. The key outcomes for multichannel format requirements so far are described in Table 1.

    High Definition Terrestrial Specification

    Dolby Digital Plus HE AAC with Transcoder

    DTG HD Digital Terrestrial (UK) √ √ (transcoder not required)

    EBU (Tech 3333) √ √

    EICTA (known as Digital Europe) √ √

    France HD DTT √ √

    Ireland HD DTT √ √

    Italy HD DTT √ √

    NorDig HD DTT (Denmark, Finland, Iceland, Norway, and Sweden) √ √

    Poland HD DTT √ RiksTV (Norwegian Terrestrial Broadcast) √

    Slovenia HD DTT √ √ Spain HD DTT √ √

    Note: DTT=Digital Terrestrial Television. Visit www.dolby.com/EuroHDTVSpecs for the latest updates.

    Table 1 Multichannel Format Requirements in European HDTV Specifications, June 2009

    Notes

    1. The EBU Project Group D/MAE states that Dolby Digital Plus and Dolby Pulse are the best candidates for broadcasting HDTV. It states that both Dolby Digital Plus and HE AAC have advantages, and a single preference cannot currently be identified. Dolby Digital (Plus) offers consistently great performance at 448 kbps and above; HE AAC offers remarkable performance where data rate is limited.

    2. The EICTA HDTV receiver specification requires Dolby Digital Plus or Dolby Pulse with transcoder output. A single universal audio solution has not been identified, so effectively both will be included unless manufacturers can be sure that a single format will be transmitted in all regions where the product is sold.

    3. Whereas an HE AAC multichannel decoder (with downmix capacity) is required from the start of the service in October 2008, an HE AAC transcoder will be required after December 31, 2009.

    4. NorDig requires dual decoders unless the operator can guarantee that a single audio format will be used within the entire market for the product.

    A New Multiformat Audio Decoding Solution

    In November 2007, Dolby Laboratories acquired Coding Technologies, the leading contributor to the HE AAC standard. Dolby intends to bring to market a new licensable audio decoder implementation that offers support for both Dolby Digital

  • 3Dolby Multistream Decoder Technical Paper

    Technical Paper

    Plus (including Dolby Digital) and Dolby Pulse decoding in a single package. This implementation will reduce the complexity and cost of integrating all audio technologies in new receivers. It will also simplify product development and testing

    while meeting current requirements for next-generation HDTV services.

    Figure 1 Block Diagram of the Multiformat Dolby MS10 Multistream Decoder for Broadcast Devices,

    TVs, and Set‑Top Boxes

    The Dolby MS10 Multistream Decoder will offer the following key benefits:

    • A universal solution that maintains flexibility for broadcasters to choose the format that best suits their requirements: Dolby Digital, Dolby Digital Plus, or Dolby Pulse.

    • Ease of implementation because deliverables, technical support, and testing are available from a single source: Dolby.

    • Reduced licensing costs compared with the existing Dolby Digital Plus, Dolby Pulse, and transcoder option.

    • Full compatibility with Dolby metadata and consumers’ existing DVD home cinema systems with all transmission formats.

    • Full multichannel support (transcoder) for Dolby Pulse in addition to Dolby Digital and Dolby Digital Plus decoding and conversion. One Dolby Digital output for all input formats.

    • Support for audio description services delivered “receiver-mix” style using two simultaneous instances of Dolby Pulse, Dolby Digital, or Dolby Digital Plus decoders, respectively—all for the price of a single decoder instance.

    • Support for multiprogram Dolby Digital Plus streams (main and associated audio delivered in the same audio stream).

    The integrated decoder/transcoder and converter combines the ability to decode Dolby Digital, Dolby Digital Plus, and Dolby Pulse within one product. All of these input signals coming into the decoders for the main audio are passed through unaltered for output over HDMI™ and S/PDIF interfaces (Dolby Digital Plus is converted to Dolby Digital; Dolby Pulse will be passed once interface definitions are final).* The signals coming into the decoders for associated audio are not passed through the system but are decoded and sent to the mixing engine instead to support the receiver-mix audio description.

    At the same time, a two-channel downmix is always created from any of the input formats in order to support decoded output (for example, for analog outputs) of a

    Dolby Digital encode

    Dolby Pulse decode

    Dolby Digital or Dolby Digital Plus or Dolby Pulse

    Stereo outputs

    Audio and metadata

    Pass-through on HDMI

    Mixing metadata

    Dolby Digital bitstream for existing home cinemas

    Dolby Digital / Dolby Digital Plus decode/convert

  • 4Dolby Multistream Decoder Technical Paper

    Technical Paper

    broadcast device. For maximum compatibility and for connectivity over S/PDIF and HDMI interfaces, a multichannel decoder for Dolby Pulse is integrated to feed an embedded Dolby Digital encoder with a multichannel signal (up to 5.1 channels), which then outputs a standard Dolby Digital bitstream (up to 5.1 channels) at a fixed bit rate of 640 kbps.

    Dolby Digital and Dolby Digital Plus inputs are handled by the integrated Dolby Digital Plus decoder/converter. This provides a two-channel downmix for decoded outputs while converting Dolby Digital Plus streams to Dolby Digital in order to provide maximum compatibility on the S/PDIF output.

    The Dolby MS10 Multistream Decoder supports simultaneous decoding of main and associated audio for Dolby Pulse and Dolby Digital/Dolby Digital Plus, respectively, to support basic two-channel mixing (Dual-Decode mode) in order to meet European broadcast specifications for next-generation audio. Audio will be mixed in an external mixing module outside of the decoder. However, the system will provide the mixing metadata potentially carried within Dolby Digital Plus as a serial bitstream on one of its outputs. This mixing metadata shall be used to control the mix in the external/system-level mixing module. The implementation of dual decoding (Dual-Decode mode) is optional but strongly recommended.

    * Transmission of Dolby Pulse streams via HDMI or S/PDIF connections will be enabled in the future as the specifications necessary to transmit the technology across these interfaces are completed.

    Comparing AAC Varieties and Dol